The 5-monocyclic aryl-1,3-dihydro-2H-1,4-benzodiazepin-2-one compounds which bear an oxygen containing substituent at position-3 of the benzodiazepine nucleus comprise an important class of medicinal agents which are useful, inter alia, as tranquilizers, anticonvulsants, and antianxiety agents. Typical of this class of compounds are 7-chloro-1,3-dihydro-3-hydroxy-5-phenyl-2H-1,4-benzodiazepine-2-one, also known as oxazepam, and 7-chloro-5-(o-chlorophenyl)-1,3-dihydro-3-hydroxy-2H-1,4-benzodiazepine-2- one, and very many others, as shown in U.S. Pat. No. 3,296,249. Although these compounds are orally active, a need exists for parental solutions of these drugs for use where oral adminstration is not feasible or desirable, such as in the case of an unconscious person, or one seriously disturbed, or where rapid onset of action is desired. Unfortunately, however, these 3-oxygenated 1,4-benzodiazepin-2-ones do not lend themselves to incorporation into the common parenteral formulations, e.g., aqueous solutions. The subject chemical compounds are themselves highly water insoluble. Further, they are so weakly basic that they do not form water soluble salts with pharmaceutically acceptable acids suitable for parenteral administration. As a result, the formulation of satisfactory parenteral preparations, which are physioligically acceptable, contain a sufficient concentration of drug to be medicinally useful, and possess sufficient chemical stability, has presented a continuing problem. U.S. Pat. Nos. 3,123,529 and 3,228,834 describe partially aqueous parenteral formulations for the benzodiazepine drugs diazepam and chlorodiazepoxide respectively (neither of which bears an oxygen containing substituent at position-3 of the benzodiazepine nucleus). Formulations of these types ae not suitable for the commercial preparation of parenteral solutions of the benzodiazepine compounds to which the present invention relates. A formula of the type described in U.S. Pat. No. 3,123,529 provides solutions of the subject benzodiazepines which are highly unstable; the 3,228,834 formula on the other hand describes a diluent which is mixed with the benzodiazepine compound only shortly before administration. The present invention, however, provides a non-aqueous parenteral solution which is highly stable on storage, may be administered directly, is physiologically acceptable, and contains medically useful amounts of drug.